All of the major heroes of the Marvel Cinematic Universe are set to play roles in Avengers: Infinity War. Could the Hulk's role be mapped to that of a hero from the Marvel Comics universe who won't be appearing in Avengers: Infinity War?
The footage released from Avengers: Infinity War so far includes a shot of Doctor Strange and Wong looking down on Bruce Banner after he apparently crashed through the roof window of the Sanctum Sanctorum. Judging by the amount of rubble surrounding Banner, it seems likely that he fell through the roof while in Hulk form and only transformed afterward, which also explains how he survived the fall.
This scene is a close reenactment of a scene from Marvel's Infinity Gauntlet #1, the first issue of the six-issue 1991 event series that serves as one of the biggest inspirations for Avengers: Infinity War. The biggest difference between the two scenes is that it isn't the Hulk who falls through Doctor Strange's roof.
Instead, it's the Silver Surfer who unceremoniously drops in Marvel's Sorcerer Supreme. Silver Surfer falls to Earth after an encounter with Thanos and finding that the Mad Titan has acquired all six Infinity Gems (what are now called Infinity Stones) and plans to wipe out half of the living beings in the universe. Surfer is the first warning that the heroes of Earth receive about Thanos's new godlike power plans to wipe out so many innocent beings.
The Hulk could be playing a similar role in Avengers: Infinity War. We already know that the Hulk will have an early encounter with Thanos that leaves him terrified, most likely aboard the Asgardian refugee ship. It would make sense if the Hulk then falls to Earth and warns Doctor Strange that Thanos is coming looking for the remaining Infinity Stones. From there, Strange could contact Iron Man, who could begin assembling the Avengers.
Silver Surfer's role in the rest of Infinity Gauntlet is to make an attempt at stealing the Infinity Gauntlet from off of Thanos's hand - an attempt that fails - and then to convince Thanos to aid in attacking Nebula after she claims the Infinity Gauntlet for herself. It seems less likely that Hulk will play those particular roles in the film, but he still remains one of the Avengers' heaviest hitters.
Avengers: Infinity War on April 27th. Black Panther is now in theaters. Other upcoming Marvel Cinematic Universe movies include Ant-Man and the Wasp on July 6th, Captain Marvel on March 8, 2019, the fourth Avengers movie on May 3, 2019, the sequel to Spider-Man: Homecoming on July 5, 2019, and Guardians of the Galaxy Vol. 3 in 2020.